The IQ3_XXS quant is good, see: huggingface.co/unsloth/DeepSeek-V4-Flash-GGUF/discussions/6
Recently also several commits to llama.cpp regarding DeepSeek-V4-Flash have landed (so now prompt processing speeds are almost doubled, KV-cache size is much smaller, and decode speed is much faster, too):
33a75f41c 2026-07-15 DeepseekV4: reduce graph splits (#25702)
7f575c39d 2026-07-14 DeepseekV4: fix seq_rm (#25588)
13f2b28b0 2026-07-11 DeepseekV4: clear cache only for seq rather than full (#25521)
00f5442cc 2026-07-11 ggml : add GGML_OP_LIGHTNING_INDEXER that implements DeepSeek V3.2/V4 lightning indexer (#24231)
2ed3c1abb 2026-07-10 llama : make all KQ masks f16 if FA is used, remove zero attention bias, remove raw_k repeats in DeepSeek V4 (#25370)
8c146a836 2026-06-29 DeepSeek V4 (#24162)