Good phpBB alternatives are Simple Machines Forum and FluxBB . True, I have not used either one or the other for a long time, but as far as I remember, plugins are installed there in a more friendly way.

SMF is convenient, but sometimes there is a very heavy hemorrhage with rights - sometimes the Apache write permission to the file disappears and you have to do it manually. Well, that's what I have, at least. And so everything is convenient and good. Usually you just unpack the plugin into a folder - and that's it. Although there are also such poop that you have to manually shove into folders. I think you need to start from plugins - look at which ones you need, for which forums they are and how they are installed where.
A well-thought-out project is the key to success)

phpbb3 has an automatic mod installer . When updating the engine, all changes in the corrected files are transferred. I have never had any conflicts during the transfer.
But I can not recommend another free forum. I think phpbb is one of the best free ones.

I myself faced a similar situation. Forum footter.com/forum is just on the latest stable version of phpbb3. It took ~10 hours to install the whole set of plugins, too long. Any automatic installers on some of the plugins display errors.
Of the free ones, I personally do not know the competitors of phpbb3, it may be worth considering ipb.

punBB