^[a-zA-Z0-9]{6}G0-[a-zA-Z0-9]{4}-[a-zA-Z0-9]{4}-1923-785FEABCD128$

Explanation:

^ matches beginning of the string

[a-zA-Z0-9]{6} matches any alphanumeric character 6 times

G0- matches that text exactly

[a-zA-Z0-9]{4}- any alphanumeric character 4 times followed by a hyphen (appears twice)

1923-785FEABCD128 matches that text exactly

$ matches the end of the string

import re

patt = re.compile('[A-Z0-9]{6}G0-[A-Z0-9]{4}-[A-Z0-9]{4}-1923-785FEABCD128')

for test in ['ABCDEFG0-GHYD-SDER-1923-785FEABCD128', 'ABCDEFH0-GHYD-SDER-0923-995FEABCD120', 'ABCDEFG0-GHYD-SDER-0923-995FEABCD120']:
    if patt.match(test):
        print(f'{test} - Valid')
    else:
        print(f'{test} - Invalid')

prints

ABCDEFG0-GHYD-SDER-1923-785FEABCD128 - Valid
ABCDEFH0-GHYD-SDER-0923-995FEABCD120 - Invalid
ABCDEFG0-GHYD-SDER-0923-995FEABCD120 - Invalid

For the sake of string-matching instead of a regex, you could use this solution:

mac_addresses = [
    'ABCDEFG0-GHYD-SDER-1923-785FEABCD128',
    'ABCDEFH0-GHYD-SDER-0923-995FEABCD120',
    'ABCDEFG0-GHYD-SDER-0923-995FEABCD120'
]

for address in mac_addresses:
    # splits 3 times, leaving the last two groups together
    # for easier string matching
    first, *_, last = address.split('-', 3)
   
    if first.endswith('G0') and last == '1923-785FEABCD128':
        match = 'Valid'
    else:
        match = 'Invalid'

    print(f"{address} - {match}")

Which prints

ABCDEFG0-GHYD-SDER-1923-785FEABCD128 - Valid
ABCDEFH0-GHYD-SDER-0923-995FEABCD120 - Invalid
ABCDEFG0-GHYD-SDER-0923-995FEABCD120 - Invalid

The benefit here? If you need to change conditions or add a new condition, you don't need to modify/keep up with a regex