Connections export file to load into QGIS using the ArcGIS REST Services feature of the Browser panel. All servers are public and do not authentication to access. This connection list is a subset of the Maryland ArcGIS REST API Services index: https://docs.google.com/spreadsheets/d/1c829bZdNqvbpoizulBU_XE5jVeNNck2kHkS-smpQ52s/edit?usp=sharing

baltimore-area_arcgis-rest-server-connections_qgis.xml

<!DOCTYPE connections>
<qgsARCGISFEATURESERVERConnections version="1.0">
    <arcgisfeatureserver authcfg="" referer="" username="" url="https://gis.aacounty.org/arcgis/rest/services" name="Anne Arundel County GIS" password=""/>
    <arcgisfeatureserver authcfg="" referer="" username="" url="https://services1.arcgis.com/mVFRs7NF4iFitgbY/arcgis/rest/services" name="BNIA-JFI Vital Signs Open Data Portal" password=""/>
    <arcgisfeatureserver authcfg="" referer="" username="" url="https://services1.arcgis.com/UWYHeuuJISiGmgXx/ArcGIS/rest/services" name="Baltimore City ArcGIS Online Assorted" password=""/>
    <arcgisfeatureserver authcfg="" referer="" username="" url="https://dotgis.baltimorecity.gov/arcgis/rest/services" name="Baltimore City DOT GIS" password=""/>
    <arcgisfeatureserver authcfg="" referer="" username="" url="https://dpwgis.baltimorecity.gov/ags102/rest/services" name="Baltimore City DPW GIS" password=""/>
    <arcgisfeatureserver authcfg="" referer="" username="" url="https://services1.arcgis.com/43Lm3JYE3nM91DAF/ArcGIS/rest/services" name="Baltimore City Department of Planning" password=""/>
    <arcgisfeatureserver authcfg="" referer="" username="" url="https://gis.baltimorecity.gov/egis/rest/services" name="Baltimore City EGIS" password=""/>
    <arcgisfeatureserver authcfg="" referer="" username="" url="https://egisdata.baltimorecity.gov/egis/rest/services" name="Baltimore City EGIS Data" password=""/>
    <arcgisfeatureserver authcfg="" referer="" username="" url="https://gisdata.baltimorecity.gov/egis/rest/services" name="Baltimore City GIS Data" password=""/>
    <arcgisfeatureserver authcfg="" referer="" username="" url="https://geodata.baltimorecity.gov/egis/rest/services" name="Baltimore City Geodata" password=""/>
    <arcgisfeatureserver authcfg="" referer="" username="" url="https://opendata.baltimorecity.gov/egis/rest/services" name="Baltimore City Open Data" password=""/>
    <arcgisfeatureserver authcfg="" referer="" username="" url="https://arcgisportal.baltimorepolice.org/gis/rest/services" name="Baltimore City Police Department GIS" password=""/>
    <arcgisfeatureserver authcfg="" referer="" username="" url="https://services3.arcgis.com/mbYrzb5fKcXcAMNi/ArcGIS/rest/services" name="Baltimore City Public School System GIS" password=""/>
    <arcgisfeatureserver authcfg="" referer="" username="" url="https://bcgis.baltimorecountymd.gov/arcgis/rest/services" name="Baltimore County GIS" password=""/>
    <arcgisfeatureserver authcfg="" referer="" username="" url="https://gis.baltometro.org/arcgis/rest/services" name="Baltimore Metropolitan Council (BMC) GIS" password=""/>
    <arcgisfeatureserver authcfg="" referer="" username="" url="https://mdpgis.mdp.state.md.us/arcgis/rest/services" name="Maryland Department of Planning GIS" password=""/>
    <arcgisfeatureserver authcfg="" referer="" username="" url="https://maps.roads.maryland.gov/arcgis/rest/services" name="Maryland Department of Transportation" password=""/>
    <arcgisfeatureserver authcfg="" referer="" username="" url="https://mdewin64.mde.state.md.us/arcgis/rest/services" name="Maryland Department of the Environment GIS" password=""/>
    <arcgisfeatureserver authcfg="" referer="" username="" url="https://gis.mdfoodsystemmap.org/server/rest/services" name="Maryland Food System Map (JHSPH Center for a Livable Future)" password=""/>
    <arcgisfeatureserver authcfg="" referer="" username="" url="https://geodata.md.gov/imap/rest/services" name="Maryland Mapping &amp; GIS Data Portal" password=""/>
</qgsARCGISFEATURESERVERConnections>