Will the bitcoin network be sustainable when the mining reward becomes zero?

Hi. I recently got into studying bitcoin, and I am unconvinced that bitcoin will be sustainable in the long-term, aka, when the mining reward becomes zero. When this happens, the only incentive for miners is the transaction fee. Would this provide enough motivation for miners to secure the network?

My understanding is that the integrity of the bitcoin network is entirely dependent on powerful computers solving hash puzzles to verify transactions (updating the ledgers/blocks). And this seems like a really arduous process that uses a lot of electricity, and creates lots of heat and noise.

I can understand why currently, mining farms would go through this difficult process given that the financial reward is so high (6.25 BTC = around $300-400k USD). But would there be a similar incentive for miners once all 21 million bitcoins have been mined? If there was, wouldn't the transaction fee be so high making bitcoin impractical for everyday transactions?

Thank you for answering my novice question.