You can combine the f for an f-string with the r for a raw string:
user="Alex"
dirToSee = fr'C:\Users\{user}\Downloads'
print (dirToSee) # prints C:\Users\Alex\Downloads
The r only disables backslash escape sequence processing, not f-string processing.
Quoting the docs:
The ‘f’ may be combined with ‘r’, but not with ‘b’ or ‘u’, therefore raw formatted strings are possible, but formatted bytes literals are not.
…
Unless an ‘r’ or ‘R’ prefix is present, escape sequences in string and bytes literals are interpreted…