-EDIT-
As Daniel Kasatchkow (below) suggested, I have attempted the following:
df._links.str.findall('qwer://abc\\\.x-data\\\.orc/v1/i/\d+/users')
But I get the following output:
0 NaN
1 NaN
2 NaN
3 NaN
4 NaN
5 NaN
...
UPDATE - Still unable to find a solution
link_reorregex_l?.characters. Also, generally you will need to capture your match with parentheses.'qwer://...'