PiTheGuy

Can confirm.

Peer-to-peer multiplayer was removed in 26.2-pre1. It’s not ready for release yet.

Code analysis (from ServerLevel.addPlayer)

Entity existing = this.getEntity(player.getUUID());
if (existing != null) {
    LOGGER.warn("Force-added player with duplicate UUID {}", player.getUUID());
    existing.unRide();
    this.removePlayerImmediately((ServerPlayer)existing, RemovalReason.DISCARDED);
}

If the existing entity isn’t a player, it still gets cast to ServerPlayer, which causes a ClassCastException. All that would need to be done to fix this is to omit the cast and replace the call to removePlayerImmediately with a call to existing.remove with the same arguments. This mirrors existing functionality but expands it to all entities.

The number of entities hit by an arrow is not stored in its NBT data,

Code Analysis

I believe the following methods are of interest. (1.20.5-rc2, decompiled with official mappings)

private void renderVehicleHealth(GuiGraphics $$0) {
        LivingEntity $$1 = this.getPlayerVehicleWithHealth();
        if ($$1 != null) {
            int $$2 = this.getVehicleMaxHearts($$1);
            if ($$2 != 0) {
                int $$3 = (int)Math.ceil((double)$$1.getHealth());
                this.minecraft.getProfiler().popPush("mountHealth");
                int $$4 = $$0.guiHeight() - 39;
                int $$5 = $$0.guiWidth() / 2 + 91;
                int $$6 = $$4;
                int $$7 = 0;
                RenderSystem.enableBlend();

                while ($$2 > 0) {
                    int $$8 = Math.min($$2, 10);
                    $$2 -= $$8;

                    for (int $$9 = 0; $$9 < $$8; $$9++) {
                        int $$10 = $$5 - $$9 * 8 - 9;
                        $$0.blitSprite(HEART_VEHICLE_CONTAINER_SPRITE, $$10, $$6, 9, 9);
                        if ($$9 * 2 + 1 + $$7 < $$3) {
                            $$0.blitSprite(HEART_VEHICLE_FULL_SPRITE, $$10, $$6, 9, 9);
                        }

                        if ($$9 * 2 + 1 + $$7 == $$3) {
                            $$0.blitSprite(HEART_VEHICLE_HALF_SPRITE, $$10, $$6, 9, 9);
                        }
                    }

                    $$6 -= 10;
                    $$7 += 20;
                }

                RenderSystem.disableBlend();
            }
        }
    }

private int getVehicleMaxHearts(@Nullable LivingEntity $$0) {
    if ($$0 != null && $$0.showVehicleHealth()) {
        float $$1 = $$0.getMaxHealth();
        int $$2 = (int)($$1 + 0.5F) / 2;
        if ($$2 > 30) {
            $$2 = 30;
        }

        return $$2;
    } else {
        return 0;
    }
}

If a vehicle has a max health of 1, (1 + 0.5) / 2 = 0.75, which gets truncated to 0 when cast to an int. Since a return value of 0 means the vehicle should display its health, the health bar is not shown.

I’m recent versions, they changed the command to allow for specific structure variants. For example you can use village_plains for a plains village. To locate a village of any type you have to use #village.

Can confirm in Release 1.17.1

Yes it is, I added it to the affected versions

Updating a pack is not Mojang's responsibility. That responsibility falls under whoever originally created the pack. Aside from that, 1.17 has only been out for a few days. Updating packs takes time and you need to be patient.