No offense but nostr coin is a terrible idea, not only because it’s an unneeded shitcoin but because it would be a security (see the LBRY case).
There’s also no need to issue eth based tokens to raise funds. You can start a business and do ordinary fundraising rounds without the need to incorporate predatory VC backed shitcoinery to create revenue streams.
Charging for the client is a solution. A one time $1-$5 payment on the App Store is simple enough (although app stores generally take a large cut)
Ad revenue is another possibility, although most people may be opposed to adverts popping up in their feeds.
Charging for certain features/services is another easy possibility.
Split payments on lightning are maybe a possibility although I’m not knowledgeable on how this would work. (Dev or relay operator gets a percentage of zaps sent on their client or relay?)
Charging for relays already happens but should probably be moved to the subscription model as you suggest.
As for the “local currency” being used for payment, this can clog the system and cause compliance issues depending on what country the receiver is in. Maybe stable coins are a better option, although at that point you might as well just use bitcoin.
I’m just spitballing these ideas. There’s really no good solution right now and dev funding is still an issue for bitcoin devs even 14 years later. I’m confident someone will think of a sound solution, but I don’t think letting tokens that will inevitably fail or be regulated to extinction, infiltrate the ecosystem is helpful in anyway.