Consider using Backblaze B2 instead. Compared to the S3 Glacier tier, B2 only costs $0.001 more per GB-month, but costs only $0.01 per GB egress (compared to AWS standard $0.09 per GB egress, plus Glacier restore fees).
S3 Glacier Deep Archive is $0.00099 per GB-month, which is about 1/5 the cost of B2 for storage, but egress fees are still high.
I put together an analysis of the cost here, and it depends how often you need to restore which will be cheaper – but the huge caveat to S3 Glacier/GDA tiers (as you point out) is that you can’t do regular repository maintenance operations.