so aside from transaction fees and rewards from newly mined blocks, are there any other methods to generate these earnings?
Are you ever hear about proof-of-person? this other methods where you can earn. but I don't know exactly works but when you running a node and open a wallet you can earning coin when the time of validation begins. you have to read this
https://idena.io/#and do you happen to know what are the methods used in the projects i mentioned in my original post please?
Tezos, matic network, cosmos, swipe and ethereum 2.0?, you need a balance for staking and earning coin, this call it Proof of stake. If you try staking proof-of-person I have mentioned above, you don't need it.