In the winter I usually perform full maintenance on my bikes and friend's bikes. This year everyone including myself has near perfect bikes. So, looking for a project bike to restore during the dark cold winter months.
There are bikes available, but if I consider resale value, there is very little out there. Once you go beyond replacing tires and cables, there is no profit, not that it's that important to me. It's not a bike I will keep, I already have too many in the stable
Many 5/10 speed bikes out there, but difficult to modernize due to hub spacing and such.
I considered transforming a hybrid or city bike to gravel, just to see how it will turn out.
Any suggestions?

how about working on unloading some of the extra bikes? sell or donate, etc?

I don't really have any extra bikes. I've already donated the ones I no longer wanted.
I have considered charitable restorations, but need to find an organization whom I can trust will give it to the truly needy

I hunted down a couple of free vintage road bikes on Craigslist and Facebook. Profit is not the end game, but quality time spent while listening to podcasts is most rewarding. Sometimes people try to sell bikes for nominal amount, but will gladly give it to you for quick hassle free pickup. Good luck.

Appreciate it. Not looking for profit, but don't want to spend too much either. There are channels on Youtube that do restorations. They'll find some of the cheapest , rusty bikes and spend dozens of hours and hundreds of dollars to restore them. I'm sure it's more the channel than resale value.
A friend brought a bike for his daughter going away to school. It's a 70's model sitting in a barn for the last 20 yrs. I'm doing a mechanical restoration, but nothing for aesthetics so as not to make it a target for thieves