ERROR 1273 (HY000) Unknown collation: utf8mb4 unicode 520 ci

ERROR 1273 (HY000) at line 25: Unknown collation: 'utf8mb4_unicode_520_ci'

https://www.digitalocean.com/community/questions/error-1273-hy000-at-line-25-unknown-collation-utf8mb4_unicode_520_ci

is correct -- this would be to a difference in database versions where the latest version you're running does not support utf8mb4unicode520_ci.

You can do a search and replace in the dump and replace instances of:

utf8mb4unicode520_ci

or

utf8mb4_unicode_520_ci

...with

utf8mb4_unicode_ci

%s/utf8mb4_unicode_520_ci/utf8mb4_unicode_ci/gc