There are a lot of us train drivers who initially wanted a flying career but saw the cost and moved our ambitions to the railways. I did mention train driving in another virus-related flying careers thread, though since this is focused non-flying careers, it's probably better that I continue here and leave the other one to aviation.
As realECMLdriver has said, there are difficulties in training new drivers at the moment. Most parts of the training process require, at some stage, delivery in a practical environment and the various parties will need time to work out how to deliver the training whilst minimising risk. Some companies are still advertising (Avanti did very recently) for trainee drivers because the recruitment process is long, it can take many months, even a good year or so. The railway is slow when it comes to recruitment.
The recruitment process usually starts with an online application/sift that may involve some fairly basic aptitude/personality tests. Take a look at the 7 Non-Technical Skills published by the Rail Safety and Standards Board (RSSB), these are highly relevant. In particular, they are looking people who value safety, stick to the rules rules and who are honest.
Next up are the main aptitude tests. To obtain a train driving licence which permits you to drive trains on Network Rail infrastructure, you must pass all of these tests. The interview referred to above where they ask you how things make you feel etc. is technically one of these tests, it's known as a Multi-Modal Interview (MMI). It's competency-based but they will put you under a lot of pressure and interrupt a lot, It's done by a psychologist so they aren't to be fooled. You must pass all of the tests (about ten I think these days) to the national standard to make it through to the next stage. One fail results in a failed sitting and if you fail two sittings you cannot re-apply as a trainee driver for any train company which uses Network Rail infrastructure. The pass rate historically was something like 10%, preparation is absolutely vital and many who pass prepare thoroughly. Many train companies set standards higher than the national minimum, however failing to meet these doesn't count towards the "two strikes and you're out" rule. Your test passes are valid for up to five years so you can take them from one company to another, few companies will recognise them for more than three years. You are not directly competing against others during these aptitude tests
Next up is usually the management interview (though some places leave the MMI till last). There's no limit as to how many you can sit though of course individual companies may prevent you from reapplying to them for say six months or a year. It's basically an exercise to see if your face fits and you are competing with others. Some places have tried to impose demographic quotas but these seem to be unpopular with drivers and local management.
The last thing is the medical, this will be arranged by your prospective employer and will be done by their provider. I'd say it's similar to a Class 2 but stricter in some areas and less so in others.
Bear in mind that train companies pay for training which in itself takes at least a year and costs the company north of £100k. In the vast majority of cases and they will expect a return of service, so only apply if you don't plan on returning to flying any time soon. Places like LNER, Avanti and Cross Country in particular tend to see very few drivers leave.
Fecking how?!?!, there are signals to follow...there are signals for learner drivers...it's not rocket science FFS, care to enlighten us what takes a years worth of training to recognise the diff between a green and a red light?