OCBC is Singaporean. The acquired Wing Hang bank (an old but relatively small local bank in HK and Macao) in 2014. They operated as OCBC Wing Hang for a few years but are now fully conformed with the Singaporean parent.
DBS is also Singaporean. So if you're OK with OCBC, it would follow that DBS is also acceptable.
SC might be one of the biggest banks headquartered in the UK, but it does over 90% of its business through its subsidiaries in Asia, Africa, and GCC/Middle East.
Citibank also has a very strong presence outside of its home in the states. But they have much stronger ties back home than SC does.
Have you tried BEA or CITIC? Chances are low but they can sometimes be friendly to non-residents. IIRC, I've seen a couple of
offshore companies banked there (that have had some connection to the region and/or owners depositing a few million HKD in personal accounts).