For a long time I used Wondershare Uniconvertor. It gets mine done in a reasonable time, even the long ones, and was only about $50 - $70 for a lifetime license. However, it has gotten pretty buggy the last few years. Lots of updates, and changes going on, all of the time. I do trust them tho. They sometimes take some time to fix issues, but they have always eventually gotten them fixed.
I have heard great things about Da Vinci Resolve, from a trusted source, however I have yet to take the time to learn it for myself. Apparently they have a really good free version available. From what I understood of the convo (sometimes tech experts, are difficult for me to understand) this free version also converts reasonably fast.
(disclaimer; I am definitely no tech expert tho, and there are many on this forum who are expert level tech)