I am thinking before 1.19.1 when chat reporting was added. 1.7 to 1.12 seem to have less requirements to run for lower end pcs. Its just some chill fun and not pvp focused so being newer than 1.9 shouldn’t matter. I am thinking 1.15 maybe since it added bees. I guess its a compromise between how well the game runs on lower hardware and what features we want.
As I said in the other comment, another option is the open source Luanti (formerly MineTest). It is a base “engine” for which you can install different community made games. There are games that attempt to copy Minecraft as completely as possible (with survival mode etc.): https://content.luanti.org/packages/?type=game
Voxelibre and mineclonia seem promising.
I will have a look into that as well. Btw while I was on minehut to check if they supported classic cube servers I noticed something odd. They have no reject cookies option which is illegal.
I just tried it myself, I can also not reject them. That’s not OK, worthy of a separate post even!