Depends. The two that I'm familiar with are probably FreeBASIC and QB64.

QB64 is pretty popular as a sort of QBASIC-dialect with additional features like OpenGL, multimedia support, etc.

FreeBasic is decent as well but its focus is more on being a compiler whereas QB64 aims to be more batteries-included with its builtin IDE.

https://github.com/QB64-Phoenix-Edition/QB64pe

https://github.com/freebasic/fbc

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JdeBP 2 hours ago | parent [-]

ThoreauBASIC has just come up on Hacker News:

* https://news.ycombinator.com/item?id=49942103

Whilst the 'Phoenix Edition' above states that the old QB64 pages are off-line, in fact there do still seem to be some around today. I don't know what the history is here. Whatever it is, it seems to have been fixed.

* https://qb64.com

* https://github.com/DualBrain/QB64

QB64 in turn points to PC-BASIC, a clone of the old GW-BASIC with at a quick glance nothing really modern going on:

* https://robhagemans.github.io/pcbasic/

	▲	vunderba 2 hours ago \| parent [-]
		My understanding is that QB64 is defacto dead and the Phoenix Edition is the continuation of the project which still receives regular updates.