If you really want to work in Spain then there is always ways to get jobs if you know where to look.
If you wish be permanently employed in Spain post-Brexit, then maybe the way to achieve this is to apply for a role that is on Spain’s shortage occupation list.
This list is updated regularly and the latest version of it is downloadable
Heres the list click here. https://www.sepe.es/SiteSepe/contenidos/empresas/profesiones_demandadas/pdf/CatalogoOcupacionesDificilCobertura.pdf
How to apply for these jobs here

New updates for residencia..
https://britishexpatsinspain.com/2021/01/08/british-expats-in-pain/