Why is your DH still giving him an allowance? Have you had a quiet, diplomatic word with him about this seriously disabling his ability to launch as an adult.
He needs to stop the allowance and simultaneously treat the resistance to applying for work as a serious problem that needs addressing.
Help him set realistic goals. First, he needs work experience urgently. Any 22yr old with none will set alarm bells ringing for employers. Get him to analyse his skills and work out which jobs might fit them, then use any connections you have to ask if he can shadow someone for a few days or do free work experience for a couple of weeks. He could also volunteer at a charity using transferable skills. Explain to him these are temporary strategies to fill his CV with relevant experience.
To earn money immediately he needs to be open to a wide variety of work, e.g walking dogs, casual labour doing a neighbour's garden (he should do yours for free every week in exchange for board and lodging, so he gets to understand how to mow, strim, prune, rake and burn leaves etc.) Get him to open wine and mix drinks if you have friends over and then he has the very basic skills to work as a waiter for catering companies that work in private homes. These are things he should have been doing in his teens. Explain that the purpose of holding down these menial jobs for a few months is to prove that he has a work ethic and is reliable and mature.
Or he might find that he is not naturally inclined to work for other people 9-5 and has more entrepreneurial aptitude. That's fine, so long as he sets something up and keeps it ticking over. DS started out buying and selling collectable items. He still has a small business doing this and it earned him as much money right through uni as having a PT job would have done. he never worked 9-5 but he did work hard - getting up early and travelling all over to sales where he knew he could find items to sell on at a good profit.
Start treating him like an adult. Expect him to clean, cook, do basic DIY at home. Expect him to do things like washing the car or helping you with tech issues as a way of contributing while he has no income. Not as punishment, but to show him you believe him capable of becoming a responsible adult who doesn't leech and cadge his way through life.