You got your answers already, that miners earn Bitcoin through solving blocks and also transactions too, these also have a advantage, securing the Bitcoin network, it doesn't end here.
Bitcoin blockchain is secured by Bitcoin miners through its hashrate and Bitcoin full nodes for relaying information of blocks and transactions to other Bitcoin nodes as well as keeping copies of Bitcoin blockchain.
Let's say all Bitcoin are mined in the future, miners won't go out of business, they will surely earn less though but transactions will still bring more rewards for them, and by that time in the future, I expect massive transactions to be happening at the time because of Bitcoin circulation.
Every 210,000 blocks, Bitcoin miners will receive 50% less bitcoin from each block reward but no thing can be predicted that its total mining revenue will be more, less or the same as in the past before a block halving. Some hypes from Ordinals and Runes shown that Bitcoin miners can sometimes earn very good amount of bitcoin from Bitcoin transaction fee.
Their income is in bitcoin but its equivalent value in fiat currency can be the same, less or more than in past market cycles as it depends on Bitcoin price. We know that Bitcoin price grows up very considerable each market cycle.