Your post reeks of scarcity mindset and beta male. You're not entirely wrong, but your mindset needs to be altered. You also failed to mention some key daygame venues such as retail stores, malls, grocery stores, and outdoor walking paths/streets as options.
Bars/Clubs---Generally no good and the odds are stacked against you
The odds are stacked against any man, and most men compound the problem by doing bar/club game in the worst way possible. Most men are going out on Friday/Saturday nights, when competition is fiercest. Additionally, when every other beta male is out there approaching women with putrid game on Friday/Saturday night, women tend to get annoyed and closed off to approaches. If a man must do bar/club game, the better choices are later nights Sun-Thurs night or 5-8 PM Happy Hour game on Monday-Thursdays.
A woman who is out at a bar at 11 PM on Tuesday night is more serious about meeting men than one out at 11 PM on Saturday night. The Friday/Saturday night crowd does a lot of attention whorring and gets annoyed by weak beta male approaches with putrid game.
Online Dating---Generally no good (unless you look like Brad Pitt) and any halfway decent looking woman is getting multiple messages a day.
This sounds like it was written in 2011 before swipe apps. Swipe apps compounded every bad trend from the 2000s/early 2010s website era of dating.
In the website era, a man was competing with other men in her inbox. Now, not only is a man competing with her swipe app inbox, he's also competing with her swipe app queue of men who could get right swiped on and be a near future volume of new messages.
The swipe apps are the worst thing that can be done.
On Instagram, it's difficult to stand out in the DMs and your own Instagram needs to be on point. You need to have more Followers than account you are Following. If you DM on LinkedIn, you're probably a desperate guy. I've never heard of a LinkedIn DM being perceived positively by any woman, but most women who are semi-active on LinkedIn get sex and date offers in their DMs. Twitter falls somewhere in between Instagram and LinkedIn.
Gym---Generally no good since the ratio is 70/30 guys and most women workout with headphones
The headphone/earbud issue is the biggest issue in gym game. The workaround to that at the gym is the fitness class scene. Fitness classes are mostly female and approaching is possible because there are no earbuds. However, even with such good ratios, it's quite difficult to get dates at fitness classes. There's a narrow window of 5 mins before and 5 mins after a class to approach. Additionally, women are not very interested in being sociable before or after classes in general.
Meetup.com---Generally no good since the ratio is not in your favor (atleast from the ones I have been to)
Most groups are awful. This is typically where desperate guys go to swarm average at best looking women.
Attractive women don't do Meetup.com groups. Attractive women do what's cool/trendy and Meetup.com has never been considered cool/trendy.
Church---Not that I have seen (but I guess it depends on your area)
Fewer younger people are active in a religion. It might work in a 50+ age bracket.
This leaves you with two main options:
1.) Your social circle---Not a woman your best friends knows but usually a friend of a friend's girlfriend's friend (or something like that)
2.) Work---You see the woman frequently and get to know her in a less superficial setting. This is especially true for couples where the female is noticeably better looking. I guarantee they either met at work or their mutual social circle.
Social circle is great for getting a girlfriend. Pay close attention to the words "a girlfriend". That means one girlfriend. If you're looking for an extended relationship (2-5 years or more), your best bet for getting that with the least amount of grief and frustration is social circle. Many men who get social circle girlfriends tend to retain those girlfriends for a long time and often beyond the useful life of the relationship. A lot of the social circle girlfriend guys are beta males and beta males operate from a scarcity mindset. It's common to see a 10 year relationship (and counting) relationship from social circle which does lead to a marriage proposal.
A social circle introduction is a higher percentage play than a swipe app interaction or approaching a stranger (either in a bar or non-bar setting). It's a more difficult path and it's not a path I recommend highly. Social circle is better in the shorter to medium term. You can get a solid, medium term (1-4 years) girlfriend via social circles more easily than through approaches or swiping more easily.
The problem with social circles becomes sustainability over a longer period of time (5+ years). Social circles have a way of getting pissed off at men who continually exchange girlfriends without marriage or babies, even if the relationships are semi-long (1-4 years). After 2 or so instances of medium term relationships, the social circle will run dry. Social circle is not likely ideal for a serial monogamist who does have extended relationships but doesn't commit or the player type who tends to have relationships of less than 1 year.
In theory, you can fix this problem with relocating and re-creating social circles every so often. In practice, that would never happen. Relocations have a way of ruining social circles. Also, after age 30 at the latest, you're not getting into a good social circle in a new city if you relocate. You can get friends if you relocate after 30 but you're not likely to get a social circle that will provide you introductions to quality girlfriends.
Dating in the workplace is even more problematic than social circle. It's possible to date within your own workplace if you have a McJob that you don't care about keeping. Men with blue collar/manual labor jobs won't have enough female co-workers to even have the option of creating a workplace romance. For men with white collar jobs, this isn't realistic. Men with white collar jobs have to be concerned about the wrath of HR if an approach goes work. Men with white collar jobs will also have to see the woman nearly every day once the interaction goes bad and it will eventually go bad. It could go bad after 1-2 dates or after a 1-2 year extended relationship. That will be unpleasant and likely force you to look for another job. It's always a major inconvenience to look for white collar jobs, regardless of economic conditions, but it is worse in recessionary times. Interview processes take a long time.
There are 3 ways to play the white collar workplace dating game.
1. Use the workplace as a part of social circle game. You could date the friends/acquaintances of your female co-workers. Everything I wrote about social circle game applies to this.
2. Approach women working in the same building as your company, but who work in other companies in that same building. This is a form of daygame cold approach. For this to actually be realistic, you typically need to work in a 10+ floor urban work building with multiple companies in the building. You'll either need to linger in common areas of the building or get some fortunate timing in riding elevators/walking through the common areas of the building. I have gotten numbers and dates by doing this option 2. With more people working at home at least part-time due to the pandemic, these types of interactions are becoming less common.
3. After you give your 2 week notice of resignation, you might be able to hit on women in your company. You might also be able to hit on women after they put in their 2 week notices. This is always challenging to do and getting more challenging with more working at home. I've never done this but I've heard of men using this tactic to get dates.
If you've already established through the grapevine that she's a normal person with no major red flags and just approach her like a colleague and see what she's about, taking it step by step, there shouldn't be any problems.
