Have been in a monogamous relationship for a while as well. I think that the rreliance on apps is a false need, cultivated to make more money on said apps as their goal isn't to lose customers by finding good matches but to keep extracting profits. There's a significant conflict of interest that makes me think that they are little more than a scam that ocassionally helps people hook-up despite the companies' best efforts.

Glad that I don't have to deal with dating and dread the idea that I may have to in the future because I hate it but my suggestions would be:

If looking to cultivate something with long-term potential, put relationship goals on the backburner and participate in an interest that has a possible social component. If one is genuinely interested, they will find people who find them interesting.

If looking to get laid, probably bars in the US (unfortunately, not usually a great place to meet people just looking to socialize, unlike Ireland or the UK).

Alternatively, if one is into kinks or curious and able to be not creepy (can be extra challenging for single men), getting involved with a kink/fetish community that does non-play meet-ups might be a good option. As noted, it can be a bit of a challenge for single men to get accepted, but is not impossible. This is because such groups tend to be very zealous about protecting their community and single men have historically been higher-risk for abuse, assault, and not honoring kink contracts. (As a man, I don't like the discrimination but do understand and agree with it as I'd rather some guy get hurt feelings than someone end up in the ICU or a dumpster).