I'm just quoting you, because I'm looking a phone, also similar to your criterias.

What I've found:

For around 2k-ish:

Honor 90 5G (2099, 12+512GB, (the RAM can be "expanded" by another 7GB)
Oppo Reno 10 Pro 5G(2199, 12+256)
OnePlus Nord 3 5G, 16+256 (the ram can be expanded up to 28GB), 2199.

All 3 will have support at least android 15, I think the OnePlus Nord 3 has support up to Android 16.

If you're going ngam ngam below 3k, some options including previous flagships open up, but if we're looking at brand new phones, these 3 pop up.

If all you care is long term OS support, the Samsung A series is the way to go. The A73 will give you 4 OS updates and 5 years of support. I don't see anything beats it (in terms of OS support)

Honorable mention: Motorola X40 / Edge 40. (the OS update is suspect, unless you can get the Lenovo Thinkphone which is a rebrand of this phone, that phone has guaranteed support up to Android 16)