Girl, we started in lockdown when she was 20 months, it seemed too good and opertunity to miss as we didn't know how long it would last. Quite a lot of accidents She always needed prompting though, I can't remember when we got out of that stage, years telling her to use the toilet.
Boy, 23 months we started. Thought we'd try it during half-term. He did really well. Different, more independent personality and we followed oh crap. He didn't like being prompted so we hardly did that. Took maybe a couple of months to be reliable. Poos were a bit of a pain. He had mild constipation, and using the potty did help a bit with that. He would not chose to sit on a potty when in nappys but wanted to be clean. If he was due a poo he'd have wee accidents. And he spent a few mornings running to and from from potty to toys when a poo was imminent. After a good poo he was really good with wees.