What are some good alternatives to Lansweeper for inventory?

PDQ Inventory looks like a good fit for that scope. It handles endpoint inventory and disk space reporting without needing to bring a ticketing system into the mix. Check the licensing against your admin count when comparing costs.

Action1 is worth a look if remote monitoring and endpoint management are useful alongside inventory. Endpoint Central is another option, particularly if you have a large environment spread across locations. I'd compare both against the actual reports you need rather than just their feature lists.

Zabbix is a strong candidate for monitoring, including low disk space alerts. I wouldn't assume it replaces a full asset inventory or configuration management database, though. You may need a separate tool if discovery and asset records matter as much as monitoring.

For broader network discovery, take a look at Armis. It can use network taps and integrations and also offers vulnerability reporting. That may be more security tooling than you need for an inventory and disk report, so get pricing before investing much time in a trial.

Before picking one, make a short list of what the current inventory actually covers. Printers, other network devices, historical software installs, and user login history can be harder to replace than a basic endpoint list.

NetBox is another name to investigate for asset records, but check its discovery and reporting capabilities against your requirements rather than assuming it's a direct replacement.