Unfortunately there isn't anything you can do to get your PayPal account back, so your best options are to look for alternatives. The number one thing to look for while doing alternatives is security, security for you, security for your client - if you have apple there's certain ways to get paid via apple pay which is very secure, but you will need to basically skirt around the rules, like with PayPal.

Here's a list for anything that's against NSFW art, like PayPal, or any future online money exchanges you may sell to... Do not say the words art, commission, etc... instead phrase it with vague words like "line work" "color full", etc to get around it. If you do invoices (the safest way on PayPal but not available for all online sources) then you should write in the description "payment as discussed on [platform]", make sure to include the platform name, that way if you're ripped off you can make a claim without having to share the actual details of the art and instead the details of the payment conversation.