Wasabi charges fees for CoinJoin transactions. Electrum probably doesn't have revenue as part of its operational structure. As for donations, this was once the reply of the developer:
Thank you for your support. I usually do not request donations for myself, because I do not think it is an effective way to incentivise free software.
Developers who request bounties tend to finish projects quickly, and do not really care about long-term maintenance.
However, you you can donate to the people who run public Electrum servers.
Electrum does relies on servers, and we currently lack an effective way to reward the server operators.
Also note that I created a company that will distribute Electrum, sell paying services to Electrum users, and fund further development of the Electrum software.
As for Exodus, it offers buy and sell and trades or swaps. Surely, they are earning from the spreads of those. After all, you cannot just swap or buy and sell coins and tokens based exactly on their actual prices in the market. There will always be a difference and that's a nice source of revenue.