For starters, the modern Dominion equipment uses a printed paper ballot. This means that every voter can (and should!) take the time to read the paper ballot that the machine produces and, if something is wrong, they can "spoil" their ballot and do it again. This is an important defense against any hypothetical tampering or malware with the software inside the machines.

After that, you're not being asked to trust machines. You're being asked to trust process. Those paper ballots travel in ballot boxes that are suitably sealed. Election officials tabulate the paper ballots with election observers and the press watching what they do. Georgia also did a risk-limiting audit (the topic of this Reddit post!) during the 2020 election which confirmed the result in the presidential race. (More details: Carter Center report, Georgia SoS's page)

As you might imagine, there's a lot more to it than I can summarize in a few paragraphs, but you should have some comfort that the combination of certification & testing, plus the use of the right kinds of policies & procedures, are where we gain confidence in our election systems.