A relatively new player as an Airtable competitor is the open source tool Baserow. If you look at their roadmap it looks very promising, but they're still in a very early phase. This means that they don’t have lots of features, which might make you hesitant to actually start using the tool instead of only trying it out.
The large advantage they hold over all the other competitors is that their software is open source, or rather open core, but let's not make it confusing. For you, this means that you can optionally install it on your own server. Goodbye vendor lock-in! In case of Baserow this also means that developers can make custom plugins and this is something that can be very useful. If you’re missing a feature with a traditional SaaS tool, you might never get it, but with an open source tool that supports custom plugins there will likely be someone who thinks the same and actually wrote that plugin. Take Wordpress as an example, there are at the time of writing 56.136 plugins on their site.
Compared to the others, their interface looks the most like Airtable. It offers the same flexibility and freedom. One of the advantages is the speed. You’ll immediately notice when you’re having lots of rows is that it’s still very fast. It seems that they’ve put a lot of effort in keeping this fast because they continuously tested with 100.000 rows. This probably means that their developers used a database with lots of rows while writing code.
Notion is one of the better alternatives to Airtable. It offers comparable flexibilities and it looks really good! The approach is different though. With Airtable you have a spreadsheet like interface that works really well with larger sets of data. Notion on the other hand has a text editor like approach.
You’ll love the flexibility! You can create a “page” and add headings, lists, text and more, just like you would expect from a text editor. The power lies in the databases you can add. You can for example add an inline table database where you can choose the fields that fits your needs. The downside compared to Airtable is that you don’t have all the features a regular database has, like linking a field to another table. Notion also doesn't work well with large amount of records, but again this is not where their focus lies. If you want to power of a database, spreadsheet and text editor in one tool then Notion will probably be your tool of choice.
Some other cool features are commenting which is great for collaboration with co-workers. Also the interactive elements like todo lists work like a charm. While it is not an open source tool that supports plugins, there are a lot of embeds you can add to your page, think of a Tweet, Google Maps and many more.
Over the last four weeks two new fields have been added, the grid view's user experience has been improved, rows can be edited via a popup and many new other features.