This book never comes up on this sub but its excellent.
Fermentation: River Cottage Handbook No.18 https://www.amazon.co.uk/dp/1408873540/ref=cm_sw_r_apan_glt_fabc_9CA5DT3T0P1KXR6E9MF7
This is a great little handbook full of simple one page recipes. Simple but not boring.
Fermentation: River Cottage Handbook No.18 https://www.amazon.co.uk/dp/1408873540/ref=cm_sw_r_awdo_navT_a_3HT1C109STFF5CA3XSQS
Worth checking world food isles too, e.g. the Tesco near here has a Polish section with a load of fermented veggies from krauts to carrots and tomatoes.
It's also very easy to make your own too, albeit with a little time commitment. A quick google: https://nourishedkitchen.com/homemade-sauerkraut/#wprm-recipe-container-21332 although I can totally recommend this book: https://www.amazon.co.uk/Fermentation-River-Cottage-Handbook-No-18/dp/1408873540/ (not all vegan recipes, although there's a vegan-specific section).
And then you find yourself subbed to r/fermentation. Good luck!