diff --git a/apps/comments/lib/Dav/CommentNode.php b/apps/comments/lib/Dav/CommentNode.php
index f90e47153bfa..6dab831d4e72 100644
--- a/apps/comments/lib/Dav/CommentNode.php
+++ b/apps/comments/lib/Dav/CommentNode.php
@@ -228,8 +228,8 @@ public function getProperties($properties) {
 
 		$result = [];
 		foreach ($properties as $property) {
-			$getter = $this->properties[$property];
-			if (\method_exists($this->comment, $getter)) {
+			$getter = $this->properties[$property] ?? null;
+			if (($getter !== null) && \method_exists($this->comment, $getter)) {
 				$result[$property] = $this->comment->$getter();
 			}
 		}
diff --git a/apps/comments/lib/Dav/EntityCollection.php b/apps/comments/lib/Dav/EntityCollection.php
index a60a6001b342..c30d08fbf592 100644
--- a/apps/comments/lib/Dav/EntityCollection.php
+++ b/apps/comments/lib/Dav/EntityCollection.php
@@ -171,7 +171,7 @@ public function childExists($name) {
 	 * @return bool
 	 */
 	public function setReadMarker($value) {
-		$dateTime = new \DateTime($value);
+		$dateTime = new \DateTime($value ?? 'now');
 		$user = $this->userSession->getUser();
 		$this->commentsManager->setReadMark($this->name, $this->id, $dateTime, $user);
 		return true;
diff --git a/apps/dav/lib/Server.php b/apps/dav/lib/Server.php
index c4e5315a00df..f40e8b988035 100644
--- a/apps/dav/lib/Server.php
+++ b/apps/dav/lib/Server.php
@@ -240,7 +240,7 @@ public function __construct(IRequest $request, $baseUri) {
 		$this->server->addPlugin(new PreviewPlugin(OC::$server->getTimeFactory(), OC::$server->getPreviewManager()));
 
 		$this->server->on('beforeMethod:PROPFIND', function (Request $request) use ($config) {
-			$depthHeader = strtolower($request->getHeader('depth'));
+			$depthHeader = strtolower((string) $request->getHeader('depth'));
 
 			if ($depthHeader === 'infinity' && !$config->getSystemValue('dav.propfind.depth_infinity', false)) {
 				throw new Exception\PreconditionFailed('Depth infinity not supported');
diff --git a/changelog/unreleased/41656 b/changelog/unreleased/41656
new file mode 100644
index 000000000000..9ada2e4a4c0b
--- /dev/null
+++ b/changelog/unreleased/41656
@@ -0,0 +1,5 @@
+Bugfix: handle deprecated code related to comments app
+
+Code paths that caused deprecation warnings in PHP 8 have been corrected.
+
+https://github.com/owncloud/core/pull/41656