Hi,
In v9 you can choose either by category or by tag. please, feel free to contact our devs in case you want to address this as a feature request. For this you can use our contact form: https://www.acymailing.com/contact/.
I have a workaround for you. Add your Joomla articles by category. Once done select the structure block that holds your Joomla content block, click on "Edit html" and look for the article tag that should look something like this:
{autoarticle:2-| display:title,intro| format:TOP_LEFT| clickable:1| clickableimg:0| wrap:100| caption:0| pict:0| autologin:0| language:any| featured:0| order:id,desc| groupbycat:0| cols:1| hpadding:10| vpadding:10| max:20}
Here you can add an extra parameter for your tags:
{autoarticle:2-| display:title,intro| format:TOP_LEFT| clickable:1| clickableimg:0| wrap:100| caption:0| pict:0| autologin:0| language:any| featured:0| order:id,desc| groupbycat:0|cols:1| hpadding:10| vpadding:10| max:20| tags:1,2,3}
Please keep in mind that everytime you make changes to the lay-out or content off the Article block in th design panel, the article tag is inserted again and you need to add the tag parameter again.