v3.5.0 Linea (59144): fresh node stuck at block 0 — FCU hangs, no EL sync

**Summary**
erigontech/erigon:v3.5.0 + Linea mainnet genesis + Maru: init OK, basic Engine API OK, but EL never leaves block 0. Can't test [#18160](https://github.com/erigontech/erigon/issues/18160) / [#20298](https://github.com/erigontech/erigon/pull/20298).

**Setup**
Genesis: [geth/geth-genesis.json](https://github.com/LFDT-Lineth/lineth-monorepo/blob/main/docs/getting-started/linea-mainnet/geth/geth-genesis.json) (59144) → 0xb6762a65…
--externalcl, mainnet bootnodes, Maru :8550 + JWT

**Works**
engine_getClientVersionV1 → 3.5.0 (~20ms)
FCU with genesis head → fast INVALID

**Broken**
FCU with non-genesis head (e.g. 0x036ee771… from #18160) → hangs ~15s
Maru: newPayload / forkchoiceUpdated TimeoutException, EL marked down
eth_blockNumber → 0x0; eth_syncing → stages: []
Log: newRoSnapshots created with empty ChainName

**Also tried (no snap path)**
--snap.skip-state-snapshot-download
--snap.p2p-manifest
Same result after 3+ min: block 0, empty stages.

**Repro**
cd docs/getting-started/linea-mainnet
docker compose run --rm erigon-init
docker compose up erigon-node maru-node

**Expected**: EL sync from scratch (P2P or execute-from-genesis) and/or FCU returns quickly, not hang.
**Question**: Recommended v3.5.0 flags for Linea mainnet from scratch? FCU hang + empty ChainName known?