To me your linked post looks completely right.
Just create new, fresh & clean strapi project. Start it.
Change the values in .env-File to abcd and restart to validate. (I wasn’t in need for this up to this point, but that would be my way how I would do it)
For generation of new keys you might want to look into supercharge/strings.
const Str = require('@supercharge/strings')
const random = Str.random()
// 'zONHF73w_4M3cmv7GZpXG'
const random_WithFiftySymbols = Str.random(50)
// 'iO3quoYg265hlzq30E8RelQc0LOKle4R0yk6CMbgeHgGNcm_mR'
Cheers